Safety device for electrical heating apparatus



Mavch 26, 1929 SAFETY DEVICE FOR ELECTRIC/A17; HEATING APPARATUS Filed Jan. 18 1927 III'IIIII idatented Mar. 26, 1929.

PATENT ()FFICE.

PATRICK MOILVENEY, OF AUCKLAND, NEW ZEALAND.

SAFETY DEVICE FOR ELECTRICAL HEATING APPARATUS.

Application filed January 18, 1827, Serial- No. 161,944, and in New Zealand December 14, 1928.

My invention relates to safet devices for electrical heating apparatus W ich are emoloyed for the purpose of automatically hreaking the circuit through the heating elements thereof when the apparatus becomes heated beyond a predetermined or required degree of temperature, and relates particularly to that class of safety devices in which, upon the apparatus becoming heated to excess, a fusible metal or allo 1s fused and the heating circuit thereby bro en.

According to the present invention, the circuit is normally retained closed by means of a contact-making member adapted to bridge contacts in the heating circuit, such contact-making member, notwithstanding the tension of spring means in the opposite direction, is held in such bridging position by a retaining piece adhered to a portion of the apparatus by a fusible adhering medium, such as solder, the arran ement being such that when the metal is iused by excessive heat, the contact-making member will, under influence of the spring means, be actuated to break the contacts, and the heatin circuit will thereby be opened and no further heat will be generated until the contacts are again bridged upon the replacement of a retaining piece.

Approved forms of carrying out the invention will now be described in detail with reference to the accompanying drawings, wherein hi ure 1, is a cross section through an electric aundry iron showing the invention applied thereto.

Figure 2, is a plan showing the contacts in the iron to which the heating elements are connected.

Figure 3, is a cross sectional elevation th gough the retaining piece and a. guiding to e.

Figure 4, is a plan of the top of the tube.

Figure 5, is an elevation showing the top portion oi the tube.

Figure 6, is an inverted plan of the top of the tube.

Figure 7, is a sectional elevation of a bridging piece and associated parts.

iiigure 8, is an inverted plan of the bridging piece.

Figure 9, is a cross sectional elevation showing an alternative method of bridging the contacts.

Figure 10, is a cross sectional elevation showing a slightly modified guide.

According to the drawings, but more articularly to Figures 1 to 8, a rod 1 is guided in a guiding tube 2, fixed in a convenient portion of the heating apparatus; in Figure 1 it is shown screwed into the cover 3 of an electric iron. The lower end of the rod 1 contains a circular bridging piece 4 insulated therefrom and bridging the contacts 5 and (3 which are arranged in the circuit of the heatin elements. The bridging piece 4 is normally held against the contacts 5 and (5 by a retaining plate 8 adhered to the top of the tube 2 by a layer of fusible metal 9, such as solder, A spring 10 is fixed at one end to any suitable position of the heating apparatus; in Figure 1 it is shown passing beneath the handle support 11 of the iron, and has its other end passing through a slot 12 in the tube 2 and through an opening 13 in the rod 1, so that when the plate 8 is freed from the top of the tube by the melting of the metal layer 9, the rod will be carried upwards by the spring 10'and the bridging piece 4; will break the contact between the contacts 5 and 6, thus breaking the circuit of the heating elements.

For convenience in again bridging the contacts 5 and 6, the plate 8 is preferably adhered by the metal layer 9 to another plate 14, having a hole through which the upper end of the rod passes, the plate 8, fusible layer 9 and the plate 14 forming a removable cap for the tube 2. This plate 14: contains hooks 15 adapted to engage beneath the flange 16 projecting outwardly from the top edge of the tube. When placing a cap in position the hooks 15 are inserted through the gaps 17 and rotated beneath the flange 16, which is tapped as at 36 to facilitate the hooks passing thereon. If desired a pin 18 proecting from the underside oi the flange will prevent the cap being rotated completely around the flange and s0 prevent the hooks again entering the gaps 17. The top of the piate 8 is formed with a recess 37 to receive the u per end of the rod which is of such a length that the end thereof must project through the plate 14 before the cap can be placed on the tube 2. Thus, when the metal 9 is once fused, a fresh cap is replaced upon the tube; Another form of cap would be as shown in Figure 10, where the bottom end of Ihe tube 2 is shown screwed into a'plug -9 and 2', is screwed into the plug 19.

The bridging piece 4 (see Figures 7 and 8) is attached to the lower end of the rod 1 as follows:

A metal disc 22 bears against a shoulder formed at the end of the rod 1, and on the underside of this plate a disc 23 of insulating material, such as mica, is placed, and then upon this a disc 24, having a projecting flange forming the circular bridging piece 4, is placed. An opening 25 in the disc 24 is sufliciently large to ensure that it will not come in contact with the rod 1. Below the disc 24 another disc 26 of insulating material, such as mica, is placed, and then a metal washer 27 over which the end of the rod 1 is riveted.

In Figure 9, an alternate form of bridging piece is shown, and consists of an arm 29 PIV- oted in a bracket 30 fixed to a convenient part of the apparatus, in this instance, to the weight block 31 of the iron. At its contact end the arm carries a separate metal contact 5 and 6 of the contact passing through any evi plate 32 insulated by insulating material 33 from the arm 29. The contact rod 1 in this case is not fixed to the bridging piece but merely rides upon the arm 29 and may have its lower end s slight depression 34 in the top of the arm as shown. The spring 10 in this case has its end carried down through an opening 35 in the cover and passes through an eye 36 on the top of the arm 29. When the plate 8 parts from the plate 14, or from the tube 2 as the case may be, the spring 10 will, through the intervention of the arm 29, break the connectlon between the contacts 5 and 6.

The contacts 5 and 6 are formed from spring leaves and are insulated from the metal weight block 31 by a sheet 38 of in sulating material, such as mica, and immediately below them a depression 39 is provided. This de ression ensures that a certain amount of exibility is given to the contacts which will enable better contact to be made by the bridging piece, and to allow for an expansion of the arts.

11 Figure 9, it will noticed that the ends pieces are turned upwards, this being merely for the purpose of making more suitable contact for the bridgin piece32. a

0 part of the device, except the actual bridging piece, at any time comes into contact with the circuit, and thus there is no danger of a short circuit from the heating circuit ce. 7 What I claim is f 1. In safety devices for electrical heating apparatus of the kind referred to, a contactightly pointed and riding 1n atacts, a rod arranged in said tube and of the other parts of the a to close the circuit by means of said contact making member adapted to bridge contacts of the heating circuit, a readily detachably and renewable portion upon the apparatus at F ortion upon t e ap aratus affected by the P lieat thereof, a retaining r when the re-.

detachplate adhered by fusible metal to said detachab1e portion, a rod interposed between such bridging piece and the retaining late whereby said bridging piece is retained against the contacts, a sprin operable uplon said bridging piece and rod whereby w en the retaining plate is released by the fusing of the fusible metal the bridgin from the contacts and break the heating circuit.

piece will move away j 3. In the device as claimed in claim 2, said spring in the form of a leaf spring attached at one end to a wall of the apparatus, a tubular guide through which said rod passes, a slot in said tubular guide, the other end of said spring passin through said a hole in sai rod.

4. In the device as claimed in claim 2, a tubular guide through which said rod passes, a flan e projecting outwardly from the upper end 0 said guide tube, a plate to which said retaining plate is adhered, and hooks upon Eaid, plate adapted to engage beneath said ange.

5. An improved safety device for electrical heatin apparatus comprising in combination a guiding tube, a retaining plate attached to the top of said guiding tube by a layer of fusible material, a contact bridgin piece, a rod arranged in said tube and adapte to close a circuit by means of said contact I bridging piece, and a spring whereby said rod is held In the circuit retaining plate against the tension of said spring.

6. 11 Improved safety device for electrical heatin A guide fixe at one end to a wall of the heatmg apparatus, a retaining-plate adhered by fusible material to the other end of said guide afi'ected by the heat of said apparatus, a contact bridging member adapted to bridge conapt/ed bridging piece and fixed to said contact bridgin piece but insulated therefrom, a spring ed to a part of the apparatus engagapparatus comprising a tubular III III

us closing position by the o .9. rod arranged in said tube and ing said rod whereby said rod is held in circuit closing position by said retaining plate against the tension of said spring.

7. An improved safety device for electrical heating apparatus comprising a guiding tube, a separate portion detachable from the upper part of said tube,.a retaining plate attached to the said separate portion by a layer of fusible material, a contact bridgingpiece,

aring retaining plate against the tension of said 1 spring.

In testimony whereof, I have signed my name to this specification.

PATRICK MOILVENEY. 

